1. Field of the Invention
The present invention relates to exposure apparatus used, for example, in fabrication process of semiconductor devices.
2. Related Background Art
The exposure apparatus used in the photolithography step for fabricating semiconductor devices is provided with a wafer loader system for performing loading and unloading of wafers. Further, the exposure apparatus is also provided with a reticle loader system for selecting a desired reticle out of a lot of reticles and setting it at an exposure position.
FIG. 11 is a plan view to show an exposure apparatus provided with a conventional wafer loader system. In this FIG. 11, an air-conditioning device 2 is set in a chamber 1 substantially isolated from the external atmosphere. Clean air blows from the air-conditioning device 2 through a vent pipe 3 and a HEPA filter (High Efficiency Particulate Air filter) 4 into the chamber 1 in the form of side flow, and the air having circulated in the chamber 1 then returns to the air-conditioning device 2 through a return (exhaust port) 5 and a vent pipe 6.
A vibration-proof table 8 is set on a floor 7 of the chamber 1. A wafer stage 10 for a wafer 11A of exposure object to be mounted thereon is set on this vibration-proof table 8. The wafer stage 10 consists mainly of a Y stage 9Y moving in the Y direction, an X stage 9X moving in the X direction, and a wafer holder 9T for holding the wafer. The wafer loader system 12 is placed beside the wafer stage 10 and on the vibration-proof table 8. The wafer loader system 12 sets (or loads) the wafer 11A on the wafer stage 10 in such a manner that a cut portion (orientation flat portion or notch portion) formed in a part of the circumference of wafer 11A is located in a predetermined positional relation relative to the wafer stage 10.
The wafer loader system 12 is constructed in such a basic arrangement that a vertical slider body 18 extending in the Y direction is fixed on a horizontal slider body 13 extending in the X direction. Two setting tables 21A and 21B are provided on a side portion of the horizontal slider body 13. Columns of storage shelves 22A and 22B for process wafers are mounted on the setting tables 21A and 21B, respectively. Wafers before exposure or wafers after exposure are stored in the columns of storage shelves 22A and 22B.
Mounted on the horizontal slider body 13 are a random access member (a wafer suction arm freely movable back and forth) 14A for taking a wafer out of the storage shelf column 22A, a random access member (a wafer suction arm freely movable back and forth) 14B for taking a wafer out of the storage shelf column 22B, a wafer hand-over member 15, and a positioning table 16, and a turn table 17 is provided on the positioning table 16. Further, a carry arm 20 is set on the horizontal slider body 13 so as to be movable in the X direction. Two carry arms 19A and 19B are provided on the vertical slider body 18 so as to be movable in the Y direction.
A wafer taken out by the random access member 14A or 14B is carried onto the turn table 17 by the carry arm 20.
FIG. 12 shows the structure of the wafer loader system 12 in FIG. 11. As shown in this FIG. 12, a position correcting device 25 is placed above the positioning table 16. (including the turn table 17). Pins (not shown) are projected from the position correcting device 25 so that they come into contact with the outer periphery of a wafer rotating on the turn table 17. A center position of wafer and a position of the cut portion are detected based on the contact state of the pins, and, based on this detection result, the center of wafer and the position of the cut portion are set each at a predetermined position. After that, the wafer on the turn table is carried to the wafer stage by the carry arm 19A.
Further, in FIG. 12, the section A shows a state wherein an in-line hand-over unit for handing over a wafer to or from a coater or a developer is provided at one end of the horizontal slider body 13. The in-line hand-over unit herein means a carrying apparatus for carrying a wafer from a coater for or applying a photoresist to the wafer, etc. to the exposure apparatus, or a carrying apparatus for carrying a wafer after exposure from the exposure apparatus to a developing apparatus (developer) etc. The section B shows a state wherein a random access member 14C and a setting table 21C having a column of wafer storage shelves are added to the wafer loader system 12. The section C shows a state wherein an in-line hand-over unit is provided at the other end of the horizontal slider body 13.
Returning to FIG. 11, a first in-line hand-over unit 23 is composed of an arm 23a and a slide shaft 23b, and a second in-line hand-over unit 24 is composed of an arm 24a, a slide shaft 24b, and a rotary member 24c. After the arm 23a of the in-line hand-over unit 23 receives a wafer 11B from a coater or a developer (not shown), the wafer 11B is handed over to the carry arm 20 at position P1 . Similarly, after the arm 24a of the in-line hand-over unit 24 receives a wafer 11C from a coater or a developer (not shown), the wafer 11C is handed over to the carry arm 20 via position P2 and position P3. Or, conversely, a wafer is handed over from the in-line hand-over unit 23 or 24 to the coater or developer (not shown).
In the above wafer loader system 12, the carry arm 20, carry arm 19A, carry arm 19B, arm 23a, arm 24a, random access members 14A, 14B, positioning table 16, and turn table 17 each were made of alumina ceramics, (containing 95 or more % of Al2O3), and plastic storage shelves (which can store twenty five wafers) mainly used in actual processes have been used as a substitute for the wafer storage shelves 22A and 22B.
In addition to the wafer loader system 12, a reticle loader system (not shown) was also set on the vibration-proof table 8. The reticle loader system is arranged to take a desired reticle out of a reticle case and to set it at the exposure position.
In the conventional technology as described above, because the wafer loader system 12 was set together with the wafer stage 10 on the vibration-proof table 8, vibration occurring upon carrying the wafer by the wafer loader system 12 was transferred to the wafer stage 10, which could degrade the positioning accuracy of wafer stage 10.
Since the wafer loader system or the reticle carrying system and the wafer stage 10 are set in the same chamber 1 actuation of the carrying mechanism can allow allowed dust to be mixed about the wafer stage 10 and can change the ambient temperature thereof.
Further, because the air conditioning of the whole inside of the chamber 1 was effected by one air-conditioning device 2 and a set of HEPA filter 4 and return 5, there were cases that necessary air-conditioning performance was not achieved at each of the exposure portion of the horizontal slider body 13 of the wafer loader system 12, and the reticle loader system, etc., or that the air conditioning exceeded specifications.
With respect to this, for example, if the wafer loader system 12 was located on the windward side of the exposure system, there were cases that particles caused by the wafer loader system 12, or a temperature change in this system negatively affected the exposure system on the leeward side.
Further, as shown in FIG. 11, when a wafer was handed over to or from the coater or developer, it was necessary to install the in-line hand-over units 23 and 24 etc. for exclusive use, which complicated the whole structure and which caused dust production because of an increase in the number of wafer hand-overs.
Also, high-accuracy positioning was difficult, because, in loading a wafer on the wafer stage 10, the wafer positioning was carried out by a method of bringing the pins actually in contact with the wafer on the turn table 17. Thus, the conventional technology required wafer re-positioning after setting the wafer on the wafer stage 10, correcting the wafer position while moving the X stage 9X or the Y stage 9Y, or by floating the wafer over the wafer stage 10 by air flow and then pushing the wafer against a positioning member, which complicated the control and caused the problem of dust production due to the air flow, etc.
Additionally, because the carry arm 20 and other components were made of alumina ceramics (containing 95 or more % of Al2O3) or a resin, there was a problem of adhesion of dust due to charge on the wafer or carry arm, etc. Similarly, because the wafer storage shelves 22A, 22B were also made of a resin for process, there were problems of adhesion of dust due to the charge as described above, access errors of wafer due to deformation of a shelf, etc.
Still further, there was another problem that when the resist dropped from the edge portion or the back surface of a wafer inside the storage shelves 22A, 22B, fine particles were adhered to wafers on lower shelves. Since an operator took out or brought in a cleaning substrate having the form of a thin disk in order to clean a wafer carrying surface and a contact surface of wafer holder 9T with the wafer, a long time period was necessary for cleaning, which lowered the apparatus operating efficiency and which caused a temperature change in the chamber or mixture of fine particles.
In view of the above-described points, an object of the present invention is to provide exposure apparatus with high reliability and high efficiency.
To achieve the above object, an exposure apparatus of the present invention may comprise a main exposure system for transferring a pattern on a mask set at a predetermined position, onto a photosensitive substrate, a substrate carrying system for loading the photosensitive substrate into the main exposure system and unloading the photosensitive substrate from the main exposure system, and a mask carrying system for loading the mask at said predetermined position and unloading the mask from said predetermined position, wherein the three systems are set in respective chambers independent of each other.
This arrangement can reduce vibration generated by the substrate carrying system or the mask carrying system, or the influence of dust etc. on the main exposure system.
To achieve the above object, an exposure apparatus of the present invention is preferably so arranged that a substrate holding hand rotatable about a predetermined axis and telescopically movable in the radial direction from said predetermined axis is provided in the substrate carrying system for loading or unloading the photosensitive substrate in or from the main exposure system for transferring the pattern on the mask, onto the photosensitive substrate, whereby this substrate holding hand is used to unload the photosensitive substrate out of the exposure system chamber or to load the photosensitive substrate from outside the exposure system chamber.
This arrangement permits hand-over of a photosensitive substrate with respect to a coater or developer etc. without separately setting an in-line hand-over unit, which can simplify the apparatus structure and which can lower production of dust etc. because of a decrease in the number of hand-over of photosensitive substrates.
Further, to achieve the above object, an exposure apparatus of the present invention is preferably so arranged that the substrate carrying system, for loading or unloading the photosensitive substrate in or from the main exposure system for transferring the pattern on the mask onto the photosensitive substrate, comprises a first carry member for carrying the photosensitive substrate in a first direction, a second carry member for carrying the photosensitive substrate in a second direction intersecting with the first direction in order to load the photosensitive substrate in the main exposure system and to unload the photosensitive substrate from the main exposure system, and a position detector for photoelectrically detecting a position of the center of the photosensitive substrate.
According to such an arrangement, the photosensitive substrate can be handed over from the first carry member to the second carry member after the center position of the photosensitive substrate is detected without contact with the photosensitive substrate and at high speed.
To achieve the above object, an exposure apparatus of the present invention comprises a main exposure system for transferring a pattern on a mask, onto a photosensitive substrate, a substrate carrying system for loading the photosensitive substrate in the main exposure system and unloading the photosensitive substrate from the main exposure system, a first base on which the main exposure system is set, and a second base, independent of the first base, on which the substrate carrying system is set.
This arrangement makes the vibration generated upon actuation of the substrate carrying system unlikely to be transferred to the main exposure system.
Further, in order to achieve the above object, an exposure apparatus of the present invention may comprise a main exposure system for transferring a pattern on a mask, onto a photosensitive substrate, a substrate carrying system for loading the photosensitive substrate in the main exposure system and unloading the photosensitive substrate from the main exposure system, a first vacuum pump for providing to hold the photosensitive substrate in the main exposure system, and a second vacuum pump independent of the first vacuum pump, for providing to hold the photosensitive substrate in the substrate carrying system.
This arrangement can prevent pressure variations caused upon suction or separation of the photosensitive substrate in the substrate carrying system from affecting the suction holding of the photosensitive substrate in the main exposure system. Conversely, when suction or separation of the photosensitive substrate is carried out in the main exposure system, the suction holding of the photosensitive substrate in the substrate carrying system will not be affected thereby, either.